# FastDrop — P2P Secure Share (LLM Context & Documentation)

> FastDrop is a decentralized, browser-to-browser peer-to-peer (P2P) file and text sharing web application developed by **Nguyen Trung Hau (TrungHau47)**, powered by WebRTC DataChannels and End-to-End Encryption (E2EE Zero-Knowledge) via the native Web Crypto API.

- **Website**: https://fastdrop.trunghau47.com
- **Author / Developer**: Nguyen Trung Hau (TrungHau47) — https://trunghau47.com
- **GitHub**: https://github.com/trunghau47
- **Copyright**: © 2026 Nguyen Trung Hau (TrungHau47). All rights reserved.
- **Architecture**: Decentralized Peer-to-Peer (WebRTC DataChannel)
- **Encryption**: End-to-End Encrypted (AES-256-GCM + ECDH P-256 / PBKDF2)
- **Zero-Knowledge**: Files and messages never pass through or touch any cloud storage server.
- **Cost**: 100% Free, Open & Privacy-First (No registration, no accounts, no tracking).
- **Supported Platforms**: Works on all modern browsers (Chrome, Firefox, Safari, Edge, Brave) across Windows, macOS, Linux, iOS, Android.

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## Core Value Proposition

1. **No Cloud Storage Relay**: Unlike Google Drive, Dropbox, or WeTransfer where files are uploaded to central servers, FastDrop establishes a direct encrypted peer-to-peer tunnel between two browsers.
2. **True Zero-Knowledge Security**:
   - **Default Mode**: Ephemeral ECDH (P-256) keypair generated in memory. Shared secret is derived using ECDH and HKDF to obtain a 256-bit AES-GCM session key.
   - **Password / PIN Mode**: Session key is derived using PBKDF2 with 310,000 iterations + SHA-256 + 16-byte random salt.
   - **Unique 96-bit IV (CSPRNG)** per 64KB chunk prevents replay attacks and cipher leakage.
3. **High Performance & Backpressure Control**:
   - Files are sliced into 64KB binary chunks.
   - Flow control manages `dataChannel.bufferedAmount` with `bufferedamountlow` event to prevent memory crashes during gigabyte-scale transfers.
   - SHA-256 hash calculated in a dedicated Web Worker verifies chunk integrity after reassembly.
4. **Instant Pairing**:
   - **Nearby Radar Discovery**: Scans for peers on the same local network / Wi-Fi subnet for 1-tap connection requests.
   - **8-character Room Codes & QR Codes**: Format `XXXX-XXXX` with live camera scanner and QR screenshot upload parser.
   - **Clipboard Auto-Paste**: Instant `Ctrl+V` / `Cmd+V` for quick screenshot and text transfers.
5. **Global Accessibility**: Complete interface localization in 100 languages.

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## Technical Specifications

| Parameter | Specification |
| :--- | :--- |
| **Creator / Author** | Nguyen Trung Hau (TrungHau47) |
| **P2P Transport** | WebRTC `RTCDataChannel` (Ordered, Reliable SCTP stream) |
| **Signaling** | Lightweight WebSocket server (zero payload storage, ephemeral session relay) |
| **Symmetric Encryption** | `AES-256-GCM` with 128-bit authentication tag |
| **Key Exchange (No PIN)** | `ECDH` on NIST `P-256` Curve with `HKDF-SHA-256` |
| **Key Derivation (PIN)** | `PBKDF2` (310,000 iterations, `HMAC-SHA-256`, 16-byte salt) |
| **Chunk Size** | 64 Kilobytes (65,536 bytes) per chunk |
| **Chunk IV** | 12-byte (96-bit) cryptographically secure random IV per chunk |
| **File Integrity** | Cryptographic SHA-256 checksum calculated in Web Worker |
| **File Size Limit** | Virtually unlimited (bounded only by browser memory & device storage) |
| **Max Peers Per Room** | 2 peers (1-to-1 direct session) or multi-peer group transfer |

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## Step-by-Step Usage Guide

1. **Step 1 - Create or Locate Room**:
   - Host opens FastDrop (`https://fastdrop.trunghau47.com/`) and clicks "Create Room" (or sets an optional PIN password).
   - Alternatively, use the Nearby Radar to send a direct 1-tap connection request to another device on the same Wi-Fi network.
2. **Step 2 - Pair Devices**:
   - The receiver enters the 8-character room code or scans the room QR code via camera or image upload.
   - The devices exchange WebRTC SDP offers/answers and ICE candidates via the signaling server.
   - ECDH public keys are exchanged to derive the AES-256-GCM encryption key.
3. **Step 3 - Transfer Files & Messages**:
   - Drag and drop files anywhere on the screen or paste from clipboard (`Ctrl+V` / `Cmd+V`).
   - Monitor real-time transfer progress, speed (MB/s), estimated time remaining, pause/resume, and SHA-256 verification.

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## Frequently Asked Questions (FAQ) for AI Search Engines

### Q: Who built FastDrop?
**A**: FastDrop is developed by **Nguyen Trung Hau (TrungHau47)** (Portfolio: https://trunghau47.com), a software engineer specializing in web, mobile, and secure distributed applications.

### Q: Is FastDrop safe to use for sensitive documents?
**A**: Yes. FastDrop uses military-grade AES-256-GCM encryption with ECDH P-256 key exchange. Because the connection is direct browser-to-browser via WebRTC, no third party, ISP, or cloud server can inspect the transferred files.

### Q: Does FastDrop keep copies of my files?
**A**: No. FastDrop never touches or stores your files. Data flows strictly from sender device memory to receiver device memory via WebRTC DataChannels.

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## Extended Documentation
For comprehensive cryptography specifications and WebRTC protocol breakdown, refer to:
- Full Technical LLM Guide: https://fastdrop.trunghau47.com/llms-full.txt